Yves Baissac

Steroid saponins from fenugreek seeds: Extraction, purification, and pharmacological investigation on feeding behavior and plasma cholesterol

The seeds of fenugreek (Trigonella foenum graecum L.) are traditionally assumed to have restorative properties. We have recently shown that a fenugreek seed extract containing steroid saponins increased food consumption and induced hypocholesterolemia in rats. This study aims to investigate the specific role of purified steroid saponins in these properties. For this purpose, an original technique for extraction and purification of steroid saponins was carried out. Thereafter, the effects of these steroid saponins were investigated on feeding behavior and metabolic endocrine changes in normal and diabetic rats. All the steroid saponins (furostanol type) were extracted from the seeds and separated from all other constituents of the entire extract by using several purification procedures to give an extract containing at least 90% of steroid saponins. Pharmcological experiments were performed in vivo in normal and streptozotocin diabetic rats: steroid saponins were administered chronically mixed with food (12.5 mg/day per 300 g body weight). Our data show that the treatment with steroid saponins significantly increased food intake and the motivation to eat in normal rats, while modifying the circadian rhythm of feeding behavior; it also stabilized the food consumption in diabetic rats, which resulted in a progressive weight gain in these animals, in contrast to untreated diabetic controls. Both in normal and diabetic rats, steroid saponins decreased total plasma cholesterol without any change in triglycerides. In conclusion, the present work reports a clear methodology to obtain all the steroid saponins and demonstrates that these saponins enhance food consumption and motivation to eat, and reduce plasma cholesterol levels in rats.

4-Hydroxyisoleucine: effects of synthetic and natural analogues on insulin secretion.

4-Hydroxyisoleucine, a peculiar amino acid extracted from fenugreek seeds and never found in mammalian tissues, exhibits interesting insulinotropic activity. To investigate the structural requirements for this stimulating effect, the insulinotropic activity of the major isomer (2S,3R,4S) of 4-hydroxyisoleucine, in the presence of 8. 3 mM glucose, was compared to that of (1) its minor isomer (2R,3R, 4S) (2) its lactone form, (3) classical structurally related amino acids, and (4) synthetic monomethylated analogues. In the isolated, ex vivo, perfused rat pancreas, only the major isomer of 4-hydroxyisoleucine (200 microM) potentiated insulin release. On incubated isolated rat islets, the threshold concentration for a significant increase (P<0.05) in insulin release was 200 microM for (2S,3R,4S) 4-hydroxyisoleucine, 500 microM for (2S,4R) and (2S,4S) gamma-hydroxynorvalines as well as (2S,3S) and (2S,3R) gamma-hydroxyvalines, and 1 mM or more for other congeners. In conclusion, the insulinotropic properties of 4-hydroxyisoleucine, in the micromolar range, are seen only in the presence of the linear major isoform; they also require carbon alpha in S-configuration, full methylation and carbon gamma-hydroxylation.

Steroid Saponins from Fenugreek and some of their Biological Properties

Fenugreek (Trigonella foenum-graecum L., Leguminosae, Trifoliae, Trigonellinae) is an annual plant found primarily in Mediterranean countries, the Middle East, and India. The seeds are most often used as a food spice (curry) and in traditional medicine. Fenugreek seeds are assumed to have restorative and nutritive properties (appetite stimulant) and hypocholesterolemic and antidiabetic effects.

Phytochemical analysis of Phyllanthus niruri L. (Phyllanthaceae) extracts collected in four geographical areas in the Democratic Republic of the Congo

This study aims at investigating the phytochemical analysis or to analyze the secondary metaboliotes of Phyllanthus niruri L. plants from four collection sites which University of Kinshasa (Unikin), National Pedagogic University of Kinshasa (UPN), Kimwenza (Kim) and Kisantu (Kis) in the Democratic Republic of the Congo (DRC). This study should give an explanation about the change of antiplasmodial activity of the same plant depending on the location of harvest. The samples of P. niruri were analyzed by thin layer chromatography (TLC) and high performance liquid chromatography (HPLC) for secondary metabolites characterizations such as of flavonoids, saponins and steroidal sapogenins and others phenolic compounds. The results revealed that UPN location presented more peaks (22) than Unikin (20), Kimwenza (15) and Kisantu (12). But Unikin location revealed more peaks (7) corresponding to major compounds than samples from others locations (UPN: 5; Kimwenza: 2 and Kisantu: 4). The peak 1 of UPN is higher (13.73) comparing to all peaks samples. The yellow-colored spots were present at all samples but those of UPN were more accentuated than all. In Kimwenza samples, two others colored spots (violet and blue) were presented. It suggested that in vitro antiplasmodial activity would be based on compounds eluted probably at the retention time around 22 min. Sometime the compounds eluted at 4.28 and 7.8 min contribute to in vitro antiplasmodial activity. The results revealed again the presence of the saponins or the steroidal sapogenins in P. niruri, made for the characterization by HPLC or by TLC probables flavonoids and presence of steroidal sapogenins.